Snap off each end of the celery stalks and remove the tough strings (you don't have to remove them all, just the ones that pull off easily).
Cut the celery into 1 inch pieces, cut on the diagonal. Dice the onion and garlic as finely as you can.
Add the butter and oil to a skillet and place on a medium heat on the stovetop. Once hot, add the celery, onion and garlic to the skillet.
Cook for 3 to 4 minutes, stirring occasionally, til the onion starts to soften.
Add the chicken stock and Italian herbs to the skillet, and place the lid on. Let the stock come up to the boil, then simmer for 5 minutes.
Take the lid off of the skillet, and add in the chopped parsley. Cook for a couple minutes more til the remaining stock has evaporated.
Serve.